Reinforced concrete coupling beam confined by discontinuous steel plates

ABSTRACT

A new type of reinforced concrete coupling beam confined by discontinuous steel plates is proposed. The proposed coupling beam confined includes longitudinal reinforcements, transverse reinforcements, concrete, and first and second web side steel plates. Longitudinal reinforcements are placed along the first direction. Transverse reinforcements are placed perpendicular to the first direction and to enclose the longitudinal reinforcements. Longitudinal reinforcements and transverse reinforcements are embedded in the concrete to form a reinforced concrete coupling beam. The reinforced concrete coupling beam has first and second surfaces opposite to each other on web sides, and third and fourth surfaces opposite to each other on flange sides. The first web side steel plate is placed on the first surface of the reinforced concrete coupling beam. The second web side steel plate is placed on the second surface of the reinforced concrete coupling beam.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Taiwan Application Serial Number 109146762, filed Dec. 30, 2020, which is herein incorporated by reference in its entirety.

BACKGROUND Field of Disclosure

The present disclosure relates to a reinforced concrete coupling beam confined by discontinuous steel plates.

Description of Related Art

Reinforced concrete structural wall or shear wall is often designed as the main component to resist lateral force due to its considerable in-plane strength and stiffness. However, practical needs sometimes require regular openings (such as openings for elevator doors or openings for daylighting windows, etc.) along the height of the wall. The openings divide the original single wall into two or more walls which are connected by beams. This system is generally called a coupled shear wall system, and the beams connecting between the walls are generally called coupling beams. When the beam's clear span-to-depth ratio is low, previous studies have indicated that diagonal reinforcements are needed to ensure certain deformation capacity of the beam.

A ratio between the clear span and the depth of the beam is called an aspect ratio. According to the current design building code for reinforced concrete structure, the reinforced concrete coupling beam with low aspect ratio and high shear strength demand must be designed with diagonal reinforcements. Although existing researches have confirmed that reinforced concrete coupling beams with diagonal reinforcements exhibit satisfactory seismic behavior, the construction of diagonal reinforcements is difficult, which adversely impacts the quality of construction and speed. Some alternatives such as the use of steel coupling beams have been proposed, but the anchorage of the steel beams in the special boundary element requires special detailing which is also difficult to deal with. Placing steel coupling beam on site with good accuracy is another challenge.

Therefore, a coupling beam that can be constructed relatively easier and faster without compromising its ductility, i.e., able to sustain the designed forces when subjected to large deformation demand, is still needed.

SUMMARY

In view of this, a new type of reinforced concrete coupling beam confined by discontinuous steel plates is proposed in the present disclosure to resolve the aforementioned issues.

This disclosure presents a reinforced concrete coupling beam confined by the discontinuous steel plates which includes longitudinal reinforcements, transverse reinforcements, concrete, a first web side steel plate, and a second web side steel plate. Longitudinal reinforcements are placed along a first direction. Transverse reinforcements are placed perpendicular to the first direction to enclose the longitudinal reinforcements. The concrete and the longitudinal reinforcements and the transverse reinforcements embedded in the concrete form a reinforced concrete coupling beam. The reinforced concrete coupling beam has a first surface and a second surface opposite to each other on web sides, and a third surface and a fourth surface opposite to each other on flange sides. The first surface, the second surface, the third surface, and the fourth surface are substantially parallel to the first direction. The first web side steel plate is placed on the first surface of the reinforced concrete coupling beam, in which a vertical projection area of the first web side steel plate on the first surface is smaller than an area of the first surface. The second web side steel plate is placed on the second surface of the reinforced concrete coupling beam, in which a vertical projection area of the second web side steel plate on the second surface is smaller than an area of the second surface.

In an embodiment of the present disclosure, the reinforced concrete coupling beam confined by the discontinuous steel plates is free of a diagonal reinforcement.

In an embodiment of the present disclosure, the concrete is not a fiber concrete.

In an embodiment of the present disclosure, the reinforced concrete coupling beam confined by the discontinuous steel plates further includes several fixing elements penetrating the first web side steel plate and the second web side steel plate.

In an embodiment of the present disclosure, the fixing elements include a screw and a nut.

In an embodiment of the present disclosure, the first surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The first web side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the first surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.

In an embodiment of the present disclosure, at least one of transverse reinforcements is placed in the first gap and the second gap.

In an embodiment of the present disclosure, on the first surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

In an embodiment of the present disclosure, the second surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The second web side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the second surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.

In an embodiment of the present disclosure, on the second surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

In an embodiment of the present disclosure, the reinforced concrete coupling beam confined by the discontinuous steel plates further includes a first flange side steel plate and a second flange side steel plate. The first flange side steel plate is placed on the third surface of the reinforced concrete coupling beam, in which a vertical projection area of the first flange side steel plate on the third surface is smaller than an area of the third surface. The second flange side steel plate is placed on the fourth surface of the reinforced concrete coupling beam, in which a vertical projection area of the second flange side steel plate on the fourth surface is smaller than an area of the fourth surface.

In an embodiment of the present disclosure, the reinforced concrete coupling beam confined by the discontinuous steel plates further includes several fixing elements penetrating the first flange side steel plate and the second flange side steel plate.

In an embodiment of the present disclosure, the fixing elements include a screw and a nut.

In an embodiment of the present disclosure, the third surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The first flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the third surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.

In an embodiment of the present disclosure, on the third surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

In an embodiment of the present disclosure, the fourth surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The second flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the fourth surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.

In an embodiment of the present disclosure, on the fourth surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:

FIG. 1 is a schematic diagram of a reinforced coupling beam structure with diagonal reinforcements, representing a comparative example compared to embodiments of the present disclosure.

FIG. 2 is a three-dimensional schematic diagram of a reinforced concrete coupling beam confined by discontinuous steel plates according to one embodiment of the present disclosure.

FIG. 3 is an exploded schematic diagram of the reinforced concrete coupling beam confined by the discontinuous steel plates according to one embodiment of the present disclosure.

FIG. 4 shows a test photo of the reinforced concrete coupling beam confined by the discontinuous steel plates after cyclic tests according to one embodiment of the present disclosure.

FIG. 5 shows a test photo of a reinforced concrete coupling beam structure with diagonal reinforcements after cyclic tests, representing a comparative example compared to embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

It should be understood that, though the technical words “the first”, “the second”, “the third” and etc. in the text can be used to describe different devices, components, areas, layers and/or parts, but the devices, components, areas, layers and/or parts should not be limited by these technical words. The technical words are used to differentiate one device, component, area, layer and/or part from others. Thus, “the first device”, “the component,” “the area,” “the layer” and/or “the part” can also be called “the second device”, “the component,” “the area,” “the layer” and/or “the part” without departing from the teaching herein.

In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings.

FIG. 1 is a schematic diagram of a reinforced coupling beam structure 10 with diagonal reinforcements, representing a comparative example compared to embodiments of the present disclosure. According to the current building code for reinforced concrete structure, the reinforced concrete coupling beam with low aspect ratio and high shear strength demand must be designed with diagonal reinforcements. As shown in FIG. 1, the reinforced coupling beam structure 10 includes longitudinal reinforcements 110, transverse reinforcement 120 confining the concrete core section, and diagonal reinforcements 130. Studies have confirmed that diagonal reinforcement is necessary for reinforced concrete coupling beams with low aspect ratio and high shear strength demand to exhibit satisfactory seismic behavior. However, diagonal reinforcements is quite difficult to construct on-site. To be specific, two groups of diagonal reinforcements that pass through each other cause severe steel congestion in the mid-span. To be developed at the critical section, those diagonal reinforcements must be inserted with certain extension into surrounding element such as boundary element of the structural wall. This is another construction challenge. In addition, building code has strict requirements for the amount and spacing of transverse reinforcements, which once again increase the difficulty of construction. All of the aforementioned construction issues adversely impact the construction quality and speed.

FIG. 2 is a three-dimensional schematic diagram of a reinforced concrete coupling beam confined by discontinuous steel plates 20 according to one embodiment of the present disclosure. FIG. 3 is an exploded schematic diagram of the reinforced concrete coupling beam confined by the discontinuous steel plates 20 according to one embodiment of the present disclosure. Referring to FIGS. 2 and 3, the reinforced concrete coupling beam confined by the discontinuous steel plates 20 includes longitudinal reinforcements 210, transverse reinforcements 220, concrete 230, a first web side steel plate 240, and a second web side steel plate 250. Longitudinal reinforcements 210 are placed along a first direction D1.

Referring to FIGS. 2 and 3, transverse reinforcements 220 are placed perpendicular to the first direction D1 and enclose the longitudinal reinforcements 210. The spacing of transverse reinforcement may be determined according to building code. In various embodiments, transverse reinforcement 220 must be closed.

Referring to FIGS. 2 and 3, longitudinal reinforcements 210 and the transverse reinforcements 220 are embedded in the concrete 230 to form a reinforced concrete coupling beam. To be specific, the reinforced concrete coupling beam has a first surface 231 and a second surface 232 opposite to each other on web sides, and a third surface 233 and a fourth surface 234 opposite to each other on flange sides. The first surface 231, the second surface 232, the third surface 233, and the fourth surface 234 are substantially parallel to the first direction D1. In various embodiments, the concrete 230 is not fiber concrete. It is noted that the “web side” mentioned herein is defined as the plane formed by the span direction and the height direction of the beam. The “flange side” mentioned herein is defined as the plane formed by the span direction and the width direction of the beam.

It is noted that the various embodiments of the reinforced concrete coupling beam confined by the discontinuous steel plates 20 does not include any diagonal reinforcements.

Referring to FIGS. 2 and 3, the first web side steel plate 240 is placed on the first surface 231 of the reinforced concrete coupling beam, and a vertical projection area of the first web side steel plate 240 on the first surface 231 is smaller than an area of the first surface 231. In various embodiments, the first surface 231 of the reinforced concrete coupling beam has a first edge 231E1 and a second edge 231E2 that are substantially perpendicular to the first direction D1, and a third edge 231E3 and a fourth edge 231E4 that are substantially parallel to the first direction D1. The first web side steel plate 240 has a first end 240E1 and a second end 240E2 that are substantially perpendicular to the first direction D1, and a third end 240E3 and a fourth end 240E4 that are substantially parallel to the first direction D1. On the first surface 231, there is a first gap G1 between the first edge 231E1 and the first end 240E1, a second gap G2 between the second edge 231E2 and the second end 240E2, a third gap G3 between the third edge 231E3 and the third end 240E3, and a fourth gap G4 between the fourth edge 231E4 and the fourth end 240E4. In various embodiments, on the first surface 231, the first gap G1 is ranged from about 2 cm to about 5 cm, the second gap G2 is ranged from about 2 cm to about 5 cm, the third gap G3 is ranged from about 2 cm to about 5 cm, and the fourth gap G4 is ranged from about 2 cm to about 5 cm.

In order to avoid clutter, the following reference numerals related to the second web side steel plate 250 and the second surface 232 are not marked in the figures. However, the corresponding positions between the elements can refer to the corresponding relationship between the first web side steel plate 240 and the first surface 231. Referring to FIGS. 2 and 3, the second web side steel plate 250 is placed on the second surface 232 of the reinforced concrete coupling beam, and a vertical projection area of the second web side steel plate 250 on the second surface 232 is smaller than an area of the second surface 232. In various embodiments, the second surface 232 has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The second web side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the second surface 232, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end. In various embodiments, on the second surface 232, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

Referring to FIGS. 2 and 3, the reinforced concrete coupling beam confined by the discontinuous steel plates 20 also includes a first flange side steel plate 260 and a second flange side steel plate 270. In order to avoid clutter, the following reference numerals related to the first flange side steel plate 260, the second flange side steel plate 270, the third surface 233, and the fourth surface 234 are not marked in the figures. However, the corresponding positions between the elements can refer to the corresponding relationship between the first web side steel plate 240 and the first surface 231. The first flange side steel plate 260 is placed on the third surface 233 of the reinforced concrete coupling beam, and a vertical projection area of the first flange side steel plate 260 on the third surface 233 is smaller than an area of the third surface 233. In various embodiments, the third surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The first flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the third surface 233, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end. In various embodiments, on the third surface 233, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

Referring to FIGS. 2 and 3, the second flange side steel plate 270 is placed on the fourth surface 234 of the reinforced concrete coupling beam, and a vertical projection area of the second flange side steel plate 270 on the fourth surface 234 is smaller than an area of the fourth surface 234. In various embodiments, the fourth surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction. The second flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction. On the fourth surface 234, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end. In various embodiments, on the fourth surface 234, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.

Referring to FIGS. 2 and 3, in various embodiments, the reinforced concrete coupling beam confined by the discontinuous steel plates 20 includes several fixing elements 280 penetrating the first web side steel plate 240 and the second web side steel plate 250. In various embodiments, the fixing elements 280 include a screw and a nut. To be specific, the screw penetrates the first web side steel plate 240 and the second web side steel plate 250, and the two ends of the screw are locked with nuts.

Referring to FIGS. 2 and 3, in various embodiments, the reinforced concrete coupling beam 20 confined by discontinuous steel plates may further include several fixing elements 290 penetrating the first flange side steel plate 260 and the second flange side steel plate 270. In various embodiments, the fixing elements 290 include a screw and a nut. To be specific, the screw penetrates the first flange side steel plate 260 and the second flange side steel plate 270, and the two ends of the screw are locked with nuts.

The fixing elements 280 and 290 and the multiple steel plates 240, 250, 260, and 270 are each used to provide a certain amount of pressure on the web side and the flange side of the reinforced concrete coupling beam. For example, the certain amount of pressure may be about 0.05 Ag×fc′ to about 0.1 Agx×fc′, wherein Ag represents an area of the confined surface of the reinforced concrete coupling beam. For the first surface, Ag here represents the surface area of the first surface, and fc′ represents a compressive strength of the concrete.

It should be noted that the web side and the flange side of the reinforced concrete coupling beam each have a central region covered by steel plates and a peripheral region, wherein the peripheral region surrounds the central region. That is to say, the width of the peripheral region is ranged from about 2 cm to about 5 cm. The reinforced concrete coupling beam confined by the discontinuous steel plates 20 can absorb damage within the peripheral region under the cyclic load (such as seismic force). In addition, it is noted that at least one of transverse reinforcements must be placed in the peripheral region (or gap) of the reinforced concrete coupling beam.

It can be understood that because the central region of the reinforced concrete coupling beam in the present disclosure is covered and fixed by the steel plates, the central region has a stronger force transmission mechanism than the peripheral region. Therefore, when the reinforced concrete coupling beam confined by the discontinuous steel plates 20 is subjected to the cyclic load (such as seismic force), the central region is likely to have less damage.

The following test results are presented to illustrate cyclic behavior of the reinforced concrete coupling beam confined by the discontinuous steel plates described in the present disclosure. This test results are in no way to be considered to limit the scope of the disclosure in any manner.

Test Results: Coupling Beam Cyclic Test

In this test, cyclic lateral displacement reversals were provided by hydraulic actuators. FIG. 4 shows a test photo of the reinforced concrete coupling beam confined by the discontinuous steel plates 20 after cyclic test according to one embodiment of the present disclosure. It can be seen from FIG. 4 that after the steel plates are removed from the reinforced concrete coupling beam confined by the discontinuous steel plates, most of the damages is concentrated within the unconfined region, while the concrete confined by the steel plates was largely undamaged.

FIG. 5 shows a test photo of a reinforced concrete coupling beam structure 10 with diagonal reinforcements after cyclic test, representing a comparative example compared to embodiments of the present disclosure. It can be seen from FIG. 5 that under a similar deformation demand, the diagonally reinforced coupling beam shows more severe and widely spread damage.

In summary, the reinforced concrete coupling beam confined by the discontinuous steel plates of the present disclosure is able to absorb most of the damage in the gap under the inevitable external load (such as earthquake). The reinforced concrete coupling beam confined by the discontinuous steel plates of the present disclosure has been proven by experiments to maintain its design strength under large deformation.

Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims. 

What is claimed is:
 1. A reinforced concrete coupling beam confined by discontinuous steel plates, comprising: longitudinal reinforcements placed along a first direction; transverse reinforcements placed perpendicular to the first direction and enclosing the longitudinal reinforcements; a concrete, wherein the longitudinal reinforcements and the transverse reinforcements are embedded in the concrete to form a reinforced concrete coupling beam which has a first surface and a second surface opposite to each other on web sides, and a third surface and a fourth surface opposite to each other on flange sides, wherein the first surface, the second surface, the third surface, and the fourth surface are substantially parallel to the first direction; a first web side steel plate placed on the first surface of the reinforced concrete coupling beam, wherein a vertical projection area of the first web side steel plate on the first surface is smaller than an area of the first surface; and a second web side steel plate placed on the second surface of the reinforced concrete coupling beam, wherein a vertical projection area of the second web side steel plate on the second surface is smaller than an area of the second surface.
 2. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 1, wherein the reinforced concrete coupling beam is free of a diagonal reinforcement.
 3. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 1, wherein the concrete is not a fiber concrete.
 4. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 1, further comprising several fixing elements penetrating the first web side steel plate and the second web side steel plate.
 5. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 4, wherein the fixing elements comprise a screw and a nut.
 6. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 1, wherein the first surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction, the first web side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction, on the first surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.
 7. The reinforced concrete coupling beam confined by the discontinuous steel plates claim 6, wherein at least one of transverse reinforcements is placed in the first gap and the second gap.
 8. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 6, wherein on the first surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.
 9. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 6, wherein the second surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction, the second web side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction, on the second surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.
 10. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 9, wherein on the second surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.
 11. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 1, further comprising: a first flange side steel plate placed on the third surface of the reinforced concrete coupling beam, wherein a vertical projection area of the first flange side steel plate on the third surface is smaller than an area of the third surface; and a second flange side steel plate placed on the fourth surface of the reinforced concrete coupling beam, wherein a vertical projection area of the second flange side steel plate on the fourth surface is smaller than an area of the fourth surface.
 12. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 11, further comprising several fixing elements penetrating the first flange side steel plate and the second flange side steel plate.
 13. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 12, wherein the fixing elements comprise a screw and a nut.
 14. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 11, wherein the third surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction, the first flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction, on the third surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.
 15. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 14, wherein on the third surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm.
 16. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 11, wherein the fourth surface has a first edge and a second edge that are substantially perpendicular to the first direction, and a third edge and a fourth edge that are substantially parallel to the first direction, the second flange side steel plate has a first end and a second end that are substantially perpendicular to the first direction, and a third end and a fourth end that are substantially parallel to the first direction, on the fourth surface, there is a first gap between the first edge and the first end, a second gap between the second edge and the second end, a third gap between the third edge and the third end, and a fourth gap between the fourth edge and the fourth end.
 17. The reinforced concrete coupling beam confined by the discontinuous steel plates of claim 16, wherein on the fourth surface, the first gap is ranged from about 2 cm to about 5 cm, the second gap is ranged from about 2 cm to about 5 cm, the third gap is ranged from about 2 cm to about 5 cm, and the fourth gap is ranged from about 2 cm to about 5 cm. 